Piezoelectric device

Abstract

A piezoelectric device includes a support substrate, an intermediate layer on the support substrate in a first region, a piezoelectric layer on the intermediate layer, a functional element on the piezoelectric layer, and an insulating layer. The insulating layer is located on the support substrate in a second region adjacent to the first region. A surface roughness of the support substrate in the second region is greater than a surface roughness of the support substrate in the first region.

What is claimed is: 
     
         1 . A piezoelectric device comprising:
 a support substrate;   an intermediate layer on the support substrate in a first region;   a piezoelectric layer on the intermediate layer;   a functional element on the piezoelectric layer; and   an insulating layer on the support substrate in a second region adjacent to the first region; wherein   a surface roughness of the support substrate in the second region is greater than a surface roughness of the support substrate in the first region.   
     
     
         2 . The piezoelectric device according to  claim 1 , wherein
 the second region includes a first portion adjacent to the first region and a second portion farther away from the first region than the first portion; and   a surface roughness of the support substrate in the first portion is greater than a surface roughness of the support substrate in the second portion.   
     
     
         3 . The piezoelectric device according to  claim 2 , wherein
 a thickness of the support substrate in the second region is smaller than a thickness of the support substrate in the first region; and   the support substrate includes an inclined region between the first region and the second region.   
     
     
         4 . The piezoelectric device according to  claim 2 , wherein
 the intermediate layer includes:
 a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and 
 a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates. 
   
     
     
         5 . The piezoelectric device according to  claim 1 , wherein
 a thickness of the support substrate in the second region is smaller than a thickness of the support substrate in the first region; and   the support substrate includes an inclined region between the first region and the second region.   
     
     
         6 . The piezoelectric device according to  claim 5 , wherein
 the intermediate layer includes:
 a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and 
 a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates. 
   
     
     
         7 . The piezoelectric device according to  claim 1 , wherein
 the intermediate layer includes:
 a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and 
 a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates.